To reduce the dependency on mineral oil based fuels, there is currently a great deal of interest in renewable fuels. The present fuel of choice for spark ignition engines is ethanol or mixtures of gasoline and ethanol. Due to the vapor phase characteristics of ethanol, engines running on pure ethanol (E100) or mixtures of ethanol and water will not start below ambient temperatures of 15° C. to 20° C. In markets where mixtures of up to 85% ethanol and gasoline (E85) are legislated, the minimum start temperature is lower at −15° C. to −20° C. In the Brazilian market (E100) minimum required start temperatures are −5° C. to −10° C. and in Sweden and North America −30° C. to −40° C. are typical requirements. This invention addresses this cold temperature start dilemma by heating the injected fuel during start. For these applications, thermal energy must be added to the fuel prior to injection.
The current solution in Brazil (E100) is to have a small underhood gasoline tank and simple cold start injector and pump to inject gasoline into the intake manifold during cold start conditions. The disadvantages of this system include fuel aging during warm months causing a no start condition when the weather gets cold, a fire risk when filling the underhood tank with a hot engine, and the necessity of a second fuel. The current solution for E85 market is a winter blend fuel of E50 or E70 and in Sweden, a block heater. The disadvantages of these solutions include the use of these vehicles in markets were there is no block heater infrastructure, such as the rest of Europe or North America or in unexpectedly cold weather when the winter blend fuel is not available.
Heated fuel injectors have been developed to heat fuel prior to injection. For example, U.S. Patent Application Publication No. 2007/0235557A1 discloses an injector that inductively heats a valve body. In addition to the very rapid heat-up of the valve body facilitated by inductive heating, the advantage of this concept is that all the fuel of the first injection is heated. That is, there is no fuel between the heater and the valve. Among the disadvantages of this concept are limited surface area available for heating (only the inside cylindrical surface of the valve body), so in spite of the rapid temperature rise of the valve body, heat up times are long due to the lack of surface area limiting power input into the fluid. In addition, heavy modifications are required to existing manufacturing equipment to manufacture the configuration.